1. Field of the Invention
This invention relates to electrified stringed musical instruments such as electric guitars, electric basses, electric pedal steel guitars, and electric violins.
2. Background of the Invention
A fundamental fact of all stringed instruments is that the strings need to be tuned to some reference pitch to produce coherent and pleasing music. For example, the accepted standard reference pitch of a 6-string guitar specifies tuning the strings to correspond with the notes E, A, D, G, B, and E corresponding to the frequencies 82.41 Hz, 110 Hz, 146.83 Hz, 196.00 Hz, 246.94 Hz, 329.63 Hz respectively. To avoid ambiguity in identifying the-strings of a guitar used in the discussion to follow, a dual nomenclature will be used of the form E(6), A(5), D(4), G(3), B(2), and E(1), where the E(6) string is the lowest pitched string, and E(1) is the highest pitched string.
Pitch drift is a problem that plagues all stringed instruments. There are many variables that affect the instrument's ability to maintain pitch over time. The unintended consequence is that the strings drift out of a state of tune. Key factors that conspire and contribute to pitch drift include variations in temperature and humidity, the materials, design, and assembly techniques used in the instrument's construction, the mechanical containment and tuning system employed, the string quality and age, and the musician's playing technique. For hundreds of years, tuning the instrument has always been accepted as routine maintenance.
Instrument builders and manufacturers continue to be challenged to create instruments that can reliably maintain their pitch. There is a tradeoff of manufacturing costs versus pitch stability. At one extreme, exotic materials and careful construction can be employed. For example, an instrument made of carbon fiber materials, precision mechanical tuners, and very high quality strings may have very good pitch stability when compared to lesser instruments. However, the price such an instrument would command would place it out of reach of most musicians. Unfortunately, it would still suffer pitch drift which can be reduced, but not eliminated. Mechanical tuning systems just cannot be made to maintain pitch over time without human interaction and correction. At the other extreme, it's a given that less expensive instruments drift more easily and require more frequent tuning adjustments.
In addition to pitch drift, another unintentional pitch problem occurs simply because some musicians are less adept than others at tuning their instrument. This is especially true if they rely on their ears alone for the tuning procedure rather than using an electronic tuning aid. Patience plays a factor. More time and effort expended on the tuning procedure usually produces better results.
Temperament is a specification for the note pitches an instrument should produce. Intonation is a measure of how well the instrument actually produces them. The instrument maker designs and fabricates the instrument to accurately produce pleasing note intervals of the chosen temperament, hoping that his efforts produce an instrument with good intonation. Attention to detail in the design phase, and good control of manufacturing tolerances typically produces an instrument capable of accurate intonation. A poorly designed and manufactured instrument may not be capable of accurate intonation due to sloppy workmanship.
Guitars and basses are designed to produce notes of the Equal Tempered chromatic scale. The nut 200 (FIG. 8), frets 201–222, and bridge saddles 872 are components of most fretted stringed instruments. These components are arranged such that the pitch of each note will be equidistant from the pitch of adjacent notes within the Equal Tempered scale. Going from one note to the next higher note, an interval of a semitone, increases the pitch by 5.95 percent.
The basic design of most fretted instruments makes slight compromises in intonation for simplicity of design. Guitars and basses use the “Rule of 18” to position the nut, frets and bridge saddles in appropriate relationships to produce reasonable Equal Temperament. This technique is not perfect. To quote from U.S. Pat. No. 5,404,783 Feiten, et al. (1995): “Unfortunately, this system is inherently deficient in that it does not result in perfect intonation. As one author stated: “Indeed, you can drive yourself batty trying to make the intonation perfect at every single fret. It'll simply never happen. Why? Remember what we said about the Rule of 18 and the fudging that goes on to make fret replacement come out right? That's why. Frets, by definition, are a bit of compromise, Roger Sadowsky observes. Even assuming you have your instrument professionally intonated and as perfect as it can be, your first three frets will always be a little sharp. The middle register—the 4th through the 10th frets—tends to be a little flat. The octave area tends to be accurate and the upper register tends to be either flat or sharp; your ear really can't tell the difference. That's normal for a perfectly intonated guitar.” (See The Whole Guitar Book, “The Big Setup,” Alan di Perna, p.17, Musician 1990.”
Intonation compensation is performed by precisely moving the bridge saddle to adjust the physical length of the vibrating portion of the string. This fine adjustment is performed as a normal setup procedure when an instrument is new. Readjustment is required over time due to many of the same environmental factors that cause pitch drift. Readjustment is also required when strings are replaced on the instrument and when other mechanical adjustments, such as a change of string height relative to the frets and fret board, occur.
Thus, common stringed instruments are a compromise between the relationships of the mechanical elements (nut, frets, and bridge saddles) plus fine mechanical adjustment to attain intonation accuracy for the specified pitch temperament.
To summarize the previous discussion on intonation and temperament, we will distinguish the three key concepts outlined above, as they will be addressed separately by the present invention:
1. Choice of temperament: There are multiple temperaments that can be used with stringed instruments. The most common are Equal Temperament, Just Temperament, and Well Temperament. Guitars, banjos, and basses commonly use Equal Temperament. Pianos commonly use Well Temperament. Just Temperament is less commonly used. There are times when the musician may want to manually alter the instrument to change pitch temperament.
2. Inherent limitations of intonation accuracy: A given instrument, even when perfectly adjusted for intonation, may still deviate from its target temperament because the instrument design was somewhat compromised to begin with. The variability of manufacturing tolerances also contributes to this problem.
3. Intonation adjustment: A given instrument may require readjustment for intonation within the temperament specification the instrument was designed for. Readjustment is necessary due to numerous environmental and mechanical factors. Intonation adjustment is considered a normal maintenance procedure.
Altered tunings are intentional pitch changes employed to perform certain musical pieces, or styles. Altered tunings may also be a preference of the musician based on musical technique and/or playing comfort. For instance, “dropped-D” tuning is commonly used with guitar, when the E(6) string is lowered two semitones to D. Another common guitar tuning is “open G” where the strings E(6) through E(1) are retuned to D-G-D-G-B-D respectively. A performing guitarist who uses altered tunings will typically employ multiple guitars, each tuned to an altered tuning pattern to avoid the inconvenience of retuning a single instrument during a performance.
Unfortunately, using an altered tuning can radically alter the string tension. On instruments with necks (guitars, basses, banjos, etc.) this changes the neck curvature and the relief of the strings to the fret board and frets, also referred to as the “action”. This can make the instrument more difficult to play, and can increase intonation error. To avoid this, instruments are typically adjusted appropriately for their altered tuning and kept that way. This is another reason many musicians employ multiple instruments in a performance, each setup for a different altered tuning.
A capo is a mechanical pitch altering device typically used on a guitar or banjo to temporarily raise the open unfretted position of play further up the fret board. A capo is shown as 860(FIG. 8) placed just behind the eighth fret 208.
A capo can produce a couple of unintentional side effects. A capo may force the instrument out of tune, as the tension on the strings may be affected depending on:                a) how tight or loose the capo is clamped onto the neck,        b) the capo's proximity and alignment to the target fret, and        c) how far up the fret board the capo is placed.        
A capo used on an instrument that has an intonation problem tends to amplify the problem because intonation error increases the further up the neck one plays. Thus, a capo can be a blessing and a curse for the musician.
Other types of mechanical pitch altering devices include bridge tremolo/vibrato units and “B-benders” for rapid pitch bend effects. Hipshot bass detuners and similar pitch altering devices are used to temporarily pitch alter one or more strings. These devices are unreliable in restoring the instrument to a state of tune after use. Tremolo/vibrato units are especially problematic in this regard. The tremolo/vibrato unit shown in 870(FIG. 8) employs a moveable bridge that typically pivots on a fulcrum and use springs to maintain string tension. The musician applies pressure to a lever 874 to momentarily bend string pitch up or down. Pitch bending devices also add considerable cost to the instrument due to the additional parts, complexities, and labor involved. Once again, this type of device can be both a blessing and a curse.
Another deliberate pitch alteration occurs when a musician tunes the instrument to a higher or lower pitch to reduce or increase the string tension. Many guitarists flatten or lower the pitch of their guitars a semitone or more to reduce the string tension slightly to improve comfort and playability. Some believe it increases volume as well. A common detuning for guitar is a half-step or semitone detuning which changes string pitch to Eb, Ab, Db, Gb, Bb, and Eb.
Numerous patents address tuning improvements to conventional guitars and related stringed instruments in the mechanical domain using bearings, improved bridge designs, improved tremolo/vibrato mechanisms and so on. However, the patents listed below do not embody the novelty, scope or the key concepts of the present invention:                U.S. Pat. No. 6,175,066 McCabe (2001)        U.S. Pat. No. 6,143,967 Smith, et al. (2000)        U.S. Pat. No. 5,986,190 Wolff, et al.(1990)        U.S. Pat. No. 5,602,353 Juszkiewicz, et al. (1997)        U.S. Pat. No. 4,899,634 Geiger (1990)        U.S. Pat. No. 4,426,907 Scholz (1984)        U.S. Pat. No. 4,383,466 Shiboya (1983)        U.S. Pat. No. 4,171,661 Rose (1979)        
Patents describing automatic tuning systems, as listed below, use electromechanical devices incorporating motors and gears or other electromechanical means to maintain pitch. A processing unit senses the string pitch in a closed-feedback system and adjusts the tension on the string using an electromechanical actuator of some type.                U.S. Pat. No. 6,437,226 Oudshoorn, et al. (2002)        U.S. Pat. No. 6,415,584 Whittall, et al. (2002)        U.S. Pat. No. 6,184,452 Long (2001)        U.S. Pat. No. 5,886,270 Wynn (1999)        U.S. Pat. No. 5,824,929 Freeland, et al. (1998)        U.S. Pat. No. 5,808,218 Grace (1998)        U.S. Pat. No. 5,767,429 Milano, et al. (1998)        U.S. Pat. No. 5,760,321 Seabert (1998)        U.S. Pat. No. 5,528,970 Zacaroli (1996)        U.S. Pat. No. 5,343,793 Pattie (1994)        U.S. Pat. No. 5,095,797 Zacaroli (1992)        U.S. Pat. No. 5,038,657 Busley (1991)        U.S. Pat. No. 5,009,142 Kurtz (1991)        U.S. Pat. No. 4,909,126 Skinn, et al. (1990)        U.S. Pat. No. 4,803,908 Skinn, et al. (1989)        U.S. Pat. No. 4,375,180 Scholz (1983)        U.S. Pat. No. 4,088,052 Hedrick (1978)        U.S. Pat. No. 4,044,239 Shumachi, et al. (1977)        
Electromechanical tuning systems suffer from several major drawbacks:                a) These systems are costly, adding hundreds of dollars to the manufacturing cost of an instrument.        b) They add mechanical complexity and weight to the instrument. There are many components that may reduce reliability of the instrument due to age, wear, and possibly neglected maintenance.        c) These systems require substantial power to operate. Large capacity batteries with their weight penalty are needed if using an onboard power supply. More typically, external power supplies are required due to the demanding power requirements.        d) These systems do not work well for applying rapid pitch alterations as they are slow to react, and may throw the instrument out of adjustment when the string tension becomes radically altered. Radical string tension alterations change the “action”. This usually makes the instrument more difficult to play, and has a negative effect on intonation accuracy as well.        e) These systems do not compensate for intonation error.        f) When applied to traditionally styled conventional instruments, these systems fundamentally alter the appearance, sound, and aesthetic appeal of these instruments.        g) These systems require additional maintenance and adjustment, usually by a trained professional thereby increasing the overall cost of ownership of the instrument.        
Several commercial products are available that implement automatic mechanical tuning of the types described by this body of work, but due to high costs, complexity, and demanding power requirements, they have not attained mass market status and instead serve a niche for certain discriminating musicians.
In U.S. Pat. No. 5,973,252 Hildebrand (1999) describes an improved method for pitch correcting a single audio signal generated from musical instruments or from the human voice using a microphone. However, the scope of Hildebrand does not address pitch altering a stringed instrument with a plurality of strings as his invention does not process a plurality of audio signals in parallel. This would be required to alter pitch for multiple strings. It does not address intonation compensation in the context of a stringed instrument. It does not address the needs and requirements of the musical performance where a musician may intentionally change the pitch of the instrument for purposes of detuning the strings, and applying alternate tunings and temperaments. The Hildebrand invention also does not include in its scope the ability to be integrated into and become part of the instrument itself with the many advantages that may result. This patent does not embody the novelty, scope or the key concepts of the present invention.
A body of work exists that addresses methods of improving intonation and applying temperament adjustments. In U.S. Pat. No. 6,426,454 Gregory (2002) describes a mechanical redesign of guitars, basses, cellos, etc. to use the “Penta” tuning system where the instrument's strings are tuned in intervals of fifths rather than intervals of fourths as in conventional guitars, basses and cellos. While interesting, this invention and the instruments designed using the Penta tuning system are unconventional and would require a musician to learn a completely new instrument with the Penta tuning and have him play with other musicians using Penta instruments and music. This is a rather draconian principle and impractical when implemented in the real world.
In U.S. Pat. No. 5,501,130 Gannon, et al. (1996) and U.S. Pat. No. 5,442,129 Mohrlok, et al. (1995) describe methods to apply “Just” temperament pitch analysis to a keyboard instrument performance. This body of work does not address issues of handling stringed instruments with a plurality of strings. Nor does it address stringed instrument pitch alteration for pitch drift, intonation compensation, pitch shifting, pitch bending, and alternate tunings.
In U.S. Pat. No. 5,404,783 (1995), U.S. Pat. No. 5,600,079 (1997), U.S. Pat. No. 5,728,956 (1998), U.S. Pat. No. 5,814,745 (1998), U.S. Pat. No. 5,955,689 (1999), U.S. Pat. No. 6,143,966 (2000), and U.S. Pat. No. 6,359,202 (2002) Feiten, et al. describe improvements to fret, nut, and bridge dimensional relationships and adjustments to the “Rule of 18” that is typically used in designing fretted guitars and basses. The result is series of temperament profiles to slightly alter the tuning of guitars and basses to make more pleasing notes. However, Feiten's invention requires alterations to a conventional guitar by adjusting the placement of the nut to a minor degree from the convention of the “Rule of 18” plus requiring subtle pitch changes to alter the temperament. How well manufacturers and musicians will accept this change has not yet been proven. However, it is unlikely that this invention will cause abandonment of instrument design parameters used for hundreds of years of guitar building.
In U.S. Pat. No. 6,359,202 (2002) Feiten describes the “Feiten Tuning Tables” which defines different sets of correction values to correct intonation for acoustic guitars, nylon stringed guitars, and steel-stringed acoustic guitars, and basses. As will become evident later, a clever engineer can apply the “Feiten Tuning Tables” to an application of the present invention.
However, the Feiten and Gannon patents discussed above do not embody the novelty, scope or the key concepts of the present invention.
A body of work encompasses pitch correction in the context of an automated music performance applicable to karaoke machines, keyboard instruments, MIDI sequencers, and “Band in a Box” computer accompaniment software. These inventions do not address the pitch problems inherent in stringed musical instruments. These inventions do not embody the novelty, scope or key concepts of the present invention:                U.S. Pat. No. 6,326,538 Kay (2001)        U.S. Pat. No. 6,166,307 Caulkins (2000)        U.S. Pat. No. 6,121,533 Kay (2000)        U.S. Pat. No. 6,121,532 Kay (2000)        U.S. Pat. No. 6,103,964 Kay (2000)        U.S. Pat. No. 6,087,578 Kay (2000)        U.S. Pat. No. 5,962,802 Iizuka (1999)        U.S. Pat. No. 5,760,326 Ishibachi (1998)        U.S. Pat. No. 5,283,388 Shimada (1994)        
A body of work encompasses pitch correction in the context of synthesized tone generation. These inventions do not address the pitch problems inherent in stringed musical instruments. These inventions do not embody the novelty, scope or key concepts of the present invention:                U.S. Pat. No. 5,763,800 Rossum (1998)        U.S. Pat. No. 5,641,931 Ogai, et al. (1997)        
A body of work encompasses pitch detection in the context of tuning devices and tuning aids for stringed instruments. In U.S. Pat. No. 4,196,652 Raskin (1980) describes an embodiment where his tuner device contains an electronic circuit to control a stepper motor to automatically tune a stringed instrument. This embodiment would fall into the category of “electromechanical tuning devices” upon which the present invention improves upon and exceeds in scope. The following tuning device inventions do not embody the novelty, scope or key concepts of the present invention:                U.S. Pat. No. 4,207,791 Murakami (1980)        U.S. Pat. No. 4,196,652 Raskin (1980)        U.S. Pat. No. 4,067,254 Deutsch (1978)        U.S. Pat. No. 3,144,802 Faber, et al. (1964)        
A commercial guitar synthesizer product family, which includes the models VG-8 and VG-88 from Roland Corporation of Japan, has a pitch correction and pitch shifting function built in. However there are several crucial limitations to these products when applied to the general problem of pitch management and control:                1. The VG-8/VG-88 devices are not built into the instrument. Instead they are external add-on peripheral systems of substantial size, weight, complexity, and cost.        2. The VG-8/VG-88 devices are designed specifically for guitar use only. They do not operate across a broad range of electric stringed instruments.        3. The VG8/VG-88 devices generally cost more than the guitars that they are intended to be used with. They generally retail in the range of $700 to $900, placing them out of reach of beginners and musicians on a budget.        4. The VG-8/VG-88 device's pitch shifting and pitch correction features are not effective when a direct guitar sound is needed. This is because the VG-8/VG-88 synthesizes sounds using the pitch and performance dynamics of the source instrument, rather than altering the source instrument's own sound for pitch.        5. The VG-8/VG-88 devices do not allow pitch shifting or temperament changes without manual programming and setup procedures.        6. The VG-8/VG-88 devices do not adjust for pitch drift in a continuous manner. The VG-8/VG-88 devices need to be placed into a calibration mode and then and only then are the string pitch correction values updated.        7. The VG-8/VG-88 devices do not provide intonation error compensation.        
Japanese patent number 2745215 publication number 09-006351 “ELECTRONIC STRINGED MUSICAL INSTRUMENT”, SHINSUKE, Roland Corp. 10-0101997, patent date Oct. 1, 1997, discusses how to pitch shift two sound sources, a synthesizer and a guitar, so that they match. This patent is specific to guitars and does not address the general category of all electric stringed instruments. In this patent, pitch shifting is performed by discrete “pitch shifter” logic, and not with a more economical and flexible solution using a general purpose processor and digital signal processing techniques. The presence of a footpedal control in drawings 2 and 6 of the patent indicates that this system is an accessory device that rests on the floor and thus is an inherently costly solution. While it addresses pitch shifting, it does not describe any ability to perform pitch shifting per string to create hybrid instruments, or to create pitch regions over the fret board. It does not address pitch bending to replace mechanical pitch bending devices on the instrument. It does not address pitch correction, nor does it address intonation compensation. It does not address the needs and requirements of the musical performance where a musician may intentionally change the pitch of the instrument for purposes of detuning the strings, and applying alternate temperaments. This patent does not embody the novelty, scope or the key concepts of the present invention.
A Japanese patent application pending review is application number 2000-220106 publication number 2002-041047 “PITCH SHIFT DEVICE”, GOUSUKE, Roland Corp dated Aug. 2, 2002. The described application is specific to a guitar, does not address the broad category of electric stringed instruments. It does describe pitch shifting for altered guitar tunings. It does describe pitch shifting to emulate guitar capo use. It does not address the ability to pitch shift individual strings to create hybrid instruments. It does not address the ability to create pitch regions on the fret board. It is an external device resting on the floor per drawing 4 of the application, intended to be foot operated. This is an inherently costly solution. It does not address pitch bending to replace mechanical pitch bending devices on the instrument. It does not address pitch correction. It does not address intonation compensation. It does not address the needs and requirements of the musical performance where a musician may intentionally change the pitch of the instrument for purposes of detuning the strings, and applying alternate temperaments. This patent application does not embody the novelty, scope or the key concepts of the present invention.